Display screen or portion thereof with transitional graphical user interface



FIG. 1 a front view of a display screen or portion thereof with transitional graphical user interface showing a first image of the claimed design;

FIG. 2 is a second image thereof; and,

FIG. 3 is a third image thereof.

The outermost broken lines in the figures show a display screen or portion thereof with transitional graphical user interface, and form no part of the claimed design. The other broken lines in the figures show portions of the transitional graphical user interface that form no part of the claimed design.

The appearance of the transitional image sequentially transitions between the images shown in FIGS. 1-3. The process or period in which one image transitions to another forms no part of the claimed design. 

CLAIM The ornamental design for a display screen or portion thereof with transitional graphical user interface, as shown and described. 